Breast microcalcifications are small (micrometer) calcium deposits that form in breast lesions. Size, number and arrangement of these deposits include important information about the malignancy and benignity of the breast lesions, making it critical to detect them in breast scans. Currently, mammography is the gold standard for detecting microcalcifications. However, in certain cases such as dense breast tissues, mammograms are ineffective and are often complemented by other modalities such as ultrasound. Ultrasound brightness (B)-scans illustrate microcalcification clusters as bright, high-contrast spots with the resolution limited by the size of speckle cells. Thus, distinguishing these reflections from speckle noise using ultrasound B-scans is also challenging.
To understand the reason for the poor performance of ultrasound in detecting microcalcifications, the inventors have previously studied the ability of the ultrasound B-mode processing in transferring diagnosis information from the patient to the B-mode image for a binary discrimination task. Information at each stage of the imaging process is defined based on an information theoretic measure, e.g., Kullback-Leibler divergence that is calculated as a distance between image data statistics under both hypotheses. Through this analysis, the inventors identified a spectrum that describes the ability of an imaging system to transfer information from an object to radio frequency (RF) data of a backscatter signal and also to the brightness (B)-mode (or other mode) image, at each spatial frequency.
Comparing the originally captured information in the RF data with the information available in the B-mode image revealed that the B-mode processing can eliminate as much as 50% of the information that can contribute to the diagnosis. These studies show that for small-area tasks such as microcalcification detection, the loss of information in the B-mode image is increased. This makes detection of microcalcifications in B-mode images quite challenging, even for a trained doctor.